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Sunday, June 23, 2013

M 51 - Whirpool Galaxy in LRGB

The Whirlpool Galaxy (also known as Messier 51a, M51a, or NGC 5194) is an interacting grand-design spiral galaxy in the constellation Canes Venatici. Recently it was estimated to be 23 ± 4 million light-years from the Milky Way Galaxy, but different methods yield distances between 15 and 35 million ly. Messier 51 is one of the best known galaxies in the sky. The galaxy and its companion (NGC 5195) are easily observed by amateur astronomers, and the two galaxies may even be seen with binoculars. The Whirlpool Galaxy is also a popular target for professional astronomers, who study it to further understand galaxy structure (particularly structure associated with the spiral arms) and galaxy interactions.

What was later known as the Whirlpool Galaxy was discovered on October 13, 1773 by Charles Messier, and is designated as M51. Its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Méchain. It was however not until 1845 that the Whirlpool became the first to be recognized as a spiral. This was achieved by Lord Rosse employing a 72-inch (~1.83 m) reflecting telescopewhich he constructed at Birr Castle, Ireland. Sometimes M51 is used to refer to the pair of galaxies, in which case the individual galaxies may be referred to as M51A (NGC 5194) and M51B (NGC 5195).

In 2005 a supernova (SN 2005cs) was observed in the Whirlpool Galaxy, peaking at apparent magnitude 14.
On 31 May 2011 a magnitude 13.5 type II supernova (SN 2011dh) was detected also in M51.